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I like Time Machine simplicity but I'd like to make it a little more space efficient: since system updates, apps updates etc change GBs, I'd like to exclude these only from older backups, keeping the last 5 or so backups full, bootable backups.

For instance: Let's say I have 3 time machine backups:

  • 2016-12-08-225622
    • Applications
    • Library
    • System
    • Users
  • 2016-12-09-225622
    • Applications
    • Library
    • System
    • Users
  • 2016-12-10-225622
    • Applications
    • Library
    • System
    • Users

I want to be able to wipe Applications, Library, System... from the first two backups and be able to keep only their latest version, in this case 2016-12-10-225622. So it would look like this after the "cleanup":

  • 2016-12-08-225622
    • Users
  • 2016-12-09-225622
    • Users
  • 2016-12-10-225622
    • Applications
    • Library
    • System
    • Users

This would be similar to excluding system files from time machine + using a boot clone, except you can get some bootable history if you want to (ie. keep the last 5 versions bootable).

It also works for other folders: what about keeping the Downloads folder history of the last month but not from the last year? This is a middle ground between excluding files and folders and keeping them.

  • I marked the question as unclear: if you don't exclude items from backups each single backup folder in the time line is fully bootable (after restoring it) - consequently you can remove all except arbitrary five of the "time stamped" folders.... Always removing the oldest of six of these folders you won't be able to recover a file accidentally deleted six hours ago though! – klanomath Dec 11 '16 at 22:41
  • I have edited it. – Yan Minari Dec 11 '16 at 22:46
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    Time Machine works with hard links! A file never changed after the initial backup only occupies its original size (and not x-times the original size with x: the number of "time stamped" backup folders) – klanomath Dec 11 '16 at 22:50
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    You need to read up on how time machine operates. You're (mostly) not seeing actual folders and files, they're just hard links pointing to various locations. Think about it, if they were all actual full backups the previous one probably woulldn't even have time to finish before the next was was due, everything would constantly be grinding to a halt and you'd run out of space within a day even with a massive backup drive. – tolgraven Dec 11 '16 at 22:53
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    So far excluding System & Apps files from backups and pairing with an up to date bootable ccc clone seems to be a reasonable choice. I would rather have a cleanup process added to time machine for simplicity though. – Yan Minari Dec 13 '16 at 2:36
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Time Machine doesn't create bootable backups in the first place, and apart from the initial one they're not "full" either.

Individual folders/files as not valid targets for tmutil delete anyways, so selectively deleting parts of snapshots like you want is not possible. But that doesn't matter much since system and app updates are infrequent enough and small enough I can guarantee they're absolutely dwarfed by your general day-to-day ~ throughput.

If you're tight on space and want to optimize what you need to do is get BackupLoupe and look for anything that frequently takes up a lot of space in your snapshots. Cache files are already excluded automatically but some apps do put stuff in ~/Library/Application Support that effectively is cache, without being marked as such. Usually gets flagged correctly eventually but I've kept some Spotify and Chrome databases excluded, for example.

  • So that means I have to use the painfully slow time machine interface to delete system files manually after major upgrades (like capitan -> sierra, adobe cc 2015 -> 2016, etc)? I thought tmutil could delete specific files and folders, like the time machine interface. – Yan Minari Dec 11 '16 at 23:41
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    No, it means you shouldn't worry about it. Maybe your situation is very different but on my machine even with heavy exclusions it pulls >1GB a day on average even during periods of lighter usage. Again, get BackupLoupe and take a look at the actual makeup of your snapshots, then work off of that. As far as larger programs go if space is an issue you could just exclude them, none of "your" stuff should be in the .app bundle anyways (unless the program has major fundamental design issues, Ableton is the only one I know that still does this) – tolgraven Dec 12 '16 at 0:03
  • I have plenty of space left on my backup disk (a 2TB tower time capsue, for a tiny 250GB SSD) but I do get results by cleaning "trash" from older backups. I may also like to keep my Downloads folder history from the last month but not from the last year. Since this is a highly volatile folder, wiping older versions will restore a considerable amount of space, that will be better used for document versioning instead. So: manual cleanup works, but is slow and tedious (and error prone!). – Yan Minari Dec 12 '16 at 3:49
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TimeMachine does cumulative backups. That means that when a file changes in time, only the changes are written plus the pointer to the older part. Let TM remove backups that are oldest and not changed(added) the longest period), this is automatically done when TM does not have enough space anymore.

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As an afterthought: when you need only a complete recent backup: why not start a new TM backup on another disk: history is gone but everything is complete from the new date.

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Time Machine is space exclusive, and will fill up the entire space before deleting the older backups. If you want to save space on the hard disk of the backup, put rather this space on a second partition.

EG you have a 2 TB disk, split it in two partition of 1TB, and affect the first partition for Time Machine, and use the second for your personal storage, or vice versa.

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